The present invention relates to an improved apparatus for the manufacture of self-locking internally threaded elements and more particularly to a device for the continuous manufacture of self-locking fasteners wherein the self-locking feature is obtained through a deformable plastic patch which is applied over a desired circumferential segment of the internal threads of the element.
In prior art patents issued to the assignee of the present invention, including U.S. Pat. No. 3,995,074 issued Nov. 30, 1976, U.S. Pat. No. 4,054,688 issued Oct. 18, 1977 and U.S. Pat. No. 4,100,882 issued July 18, 1978, there is disclosed apparatus and methods for applying locking patches of resilient resin to internally threaded articles such as nuts, having openings at both ends of the threaded portions. In the devices disclosed in these patents, generally a rotatable table is disposed for receiving fasteners about the periphery of the table and transporting them through a plurality of stations to effect application of the patch to the internal threads of the fastener elements.
In U.S. Pat. Nos. 4,054,688 and 4,100,882 there is provided a means whereby a portion of the heat fusible resin particles is deposited on one area of the hot threaded surface of an element, and thereafter, resin particles are deposited on a further area of the threaded surface to produce two distinct patches at a desired location. In each of the aforementioned patents, the internally threaded element is retained on the rotatable support member in a selected position by means of a slot which receives a portion of the external hex of a hex headed nut, by way of example. After a discrete patch is applied to the internal threads of the fastener, a turning moment is applied to the fastener element to move it such that a different external surface of the hexagonal element is received the slot, after which a second discrete patch is applied to the fastener U.S. Pat. No. 3,416,492, issued Dec. 17, 1968, shows a device for holding a threaded fastener and applying a coating through 360.degree. of threads thereon.
While the above referred to apparatus and methods have proved to be successful in achieving the objects for which they were intended, the particular devices and methods disclosed are directed to the application of one or more discrete patches to the internal threads of an element.
It has been found that there are applications in which it becomes desirable to apply a continuous circumferential locking patch to the internal threads of the fastener element. In many instances, it has been regarded that the locking patch be applied through the entire 360 degree arc of the internal threads in uniform manner, while other applications may require a lesser angle of patch to be applied to the threads. To accomplish this, it is necessary to uniformly rotate the fastener element through at least the desired angle of application, while resin particles are being directed against the threaded surface only during the desired angle of application, to build up deposits on the required areas.
It is therefore an object of the present invention to provide a method and apparatus for the manufacture of self-locking internally threaded elements wherein the locking body of resilient resin is applied over a desired arcuate portion of the internal threads.
It is a further object of the invention to provide a method and apparatus wherein a self-locking internally threaded element is manufactured having a locking body of resilient resin provided over 360 degrees of arc of the internal threaded surface.